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UNITED STATES PATENT OFFICE.

CHARLES II. VILDER, OF NATICK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO FREDERICK E. ATTEAUX, TRUSTEE, OF BOSTON, MASSACHUSETTS.

MoLn.

SPECIFICATION. forming part of Letters Patent No. 404,372, dated May 28, 1889.

Application filed May 4, 1888. Serial No. 273,002. (No model.)

Q To all whom it may concern:

Be it known that I, CHARLES H. IVILDER, of Natick, in the county of Middlesex and State of Massachusetts, a citizen of the United States, have invented certain new and useful Improvements in the Manufacture of Molds for Metallic Castings, of which the following is a specication.

My invention relates to an improvement in the formation of molds from which to cast metal articles, and its object is to produce a mold such that its inner or molding-surface will not bein any degree fused or iiuxed by the contact of the molten metal, but will at all times have and preserve a smooth and indestructible molding-face, whereby not only can more perfect castings be obtained than has heretofore been possible, but also the same mold maybe repeatedly used for producing castings.

My invention also includes a convenient form in which the mold can be made and thereby preserved against accidental injury in handling, all as will be hereinafter more fully set forth and explained.

For the further explanation of my invention I have shown in the accompanying drawings at Figure l, one part of a flask and one part of a mold for a cylindrical casting, and a cylinder of cast metal in the mold, part of the casting which would be formed in the other part of the mold being above the surface in the part of the mold shown. Fig. 2 shows a transverse section on the line 2 2 of Fig. l of the flask, mold, and casting.

The outer wall of flask is marked a, the mold is marked a, and the casting is marked a2.

' The mold is represented in the drawings as composed of two parts, the inner portion, a3, being formed of my improved mold material, and the outer portion of a strengthening or protecting material, as will be hereinafter explained. A layerof sand is represented at a4 between the mold and the outer wall of the flask. The customary dowels and sockets for joining adjacent portions of the mold are represented at a5, and flanges a are provided on the edges of the flask to retain the sand be tween the mold and flask.

My improved mold is formed of a mixture of pulverized coke and pulverized graphite;

or, as it is commercially known, plumbago. In preparing this mixture I grind each of the substances to as ne a powder as is readily practicable, the graphite, as is well known, being capable of a considerably finer reduction than the coke. After the two substances have been thus ground I unite or incorporate them with each other mechanically in any convenient manner. The function of the coke in the mixture thus formed is that which comes from its refractory and infusible character. The function of the graphite is through its equally refractory character and through its much greater fineness of grain to fully permeate and fill up the interstices that would otherwise occur among the grains of coke, thus giving to the mixture as a whole a much more compact texture or grain, and consequently much greater capacity for exactly preserving and reproducing the form of the article to be cast than would be possible if coke alone were employed.

The mixture of coke and graphite above described may be used in the lsame manner as common molding-sand is now employed, and forms the subject-matter of another application for patent. Inasmuch, however, as a mold, if made in the ordinary manner by a pattern in a loose mixture such as has been described, is readily disturbed and destroyed by handling, I "prefer in using my improved mixture for molding to give to the mold a permanent form. This I do by mixing with a suitable portion of the coke and graphite mixture a suitable plastic cokable binder-such as melted pitch or tar-in sufficient proportion to make the whole mass plastic. The plastic mass thus obtained may be pressed or tamped around the article or pattern duplicates of which the mold is intended to produce. Then the interior face of the mold has thus been given the desired form and after it has cooled, in order to make it permanent and convenient for repeated handling, I place the mold within a suitable metal box or case and surround it. therein with sand. This box is then closed, placed in a heating-furnace, and subjected to heat at a temperature and for a period sufficient to convert the binder into coke. The

mold then, after being allowed to cool, may be repeatedly used in the ordinary manner to IOO furnish castings of the form originally inipressed upon it, as before explained. The permanent or portable mold thus obtained will sometimes, however, be found to lack the strength required to withstand the handling to which it may be subjected; therefore, to meet this defect, I may provide it with an eX- terior or backing, as Iwill now proceed to describe.

After the mixture of coke, graphite, andthe binder has been pressed or tamped upon the pattern l take a sufficient quantity of pulverizcd coke and mix it with an adhesive cokable binder, thus forming a second plastic mass; and this second mass I spread over the back or outer portion of the mold formed of coke and graphite bound together, and temporarily unite the two under moderate pressure while the mass of the backing is still plastic. I then place the combined mold and backing in a sand-iilled case and subject the whole to the coking operation in a furnace, as before described, continuing this until the whole of the binder throughout the mass has been converted to coke, thereby prod ueing a mold formed of a mixture of coke and graphite, and a backing for the mold formed of coke, the whole integrally united.

It will be understood that a mold so formed will be used in casting in the ordinary manner, the molds being made sectional and provided with dowels and sockets or other wellknown appropriate devices for uniting` them in readiness for casting, and a flask and sand iilling being applied in the usual manner.

I claiml. As a new article of manufacture a permanent mold formed of coke, graphite, and a coked binder, as described.

2. As a new article of manufacture, a permanent mold provided with an integrallyattached back, the face of the said mold being formed of a mixture of coke, giaphite, and coked' binder, all substantially as described, and the backing of said mold being formed of coke and a cokcd binder, the said mold and back being united, substantially as set forth.

CHARLES ll. VILDER. lvitnesses:

IIoUGi-rroN, NVM. E. PEABODY. 

